Do more conservative URL normalization

.rubocop.yml

@@ -1,6 +1,7 @@
 inherit_from:
   - .rubocop_todo.yml
   - .rubocop/layout.yml
+  - .rubocop/metrics.yml
   - .rubocop/style.yml
 
 AllCops:

.rubocop/metrics.yml

@@ -0,0 +1,4 @@
+Metrics/BlockLength:
+  Exclude:
+    - 'spec/**/*.rb'
+    - '*.gemspec'

lib/http/uri.rb

@@ -37,15 +37,18 @@ class URI
     # @private
     HTTPS_SCHEME = "https"
 
+    # @private
+    PERCENT_ENCODE = /[^\x21-\x7E]+/.freeze
+
     # @private
     NORMALIZER = lambda do |uri|
       uri = HTTP::URI.parse uri
 
       HTTP::URI.new(
         :scheme    => uri.normalized_scheme,
         :authority => uri.normalized_authority,
-        :path      => uri.normalized_path,
-        :query     => uri.query,
+        :path      => uri.path.empty? ? "/" : percent_encode(Addressable::URI.normalize_path(uri.path)),
+        :query     => percent_encode(uri.query),
         :fragment  => uri.normalized_fragment
       )
     end
@@ -71,6 +74,19 @@ def self.form_encode(form_values, sort = false)
       Addressable::URI.form_encode(form_values, sort)
     end
 
+    # Percent-encode all characters matching a regular expression.
+    #
+    # @param [String] string raw string
+    #
+    # @return [String] encoded value
+    #
+    # @private
+    def self.percent_encode(string)
+      string&.gsub(PERCENT_ENCODE) do |substr|
+        substr.encode(Encoding::UTF_8).bytes.map { |c| format("%%%02X", c) }.join
+      end
+    end
+
     # Creates an HTTP::URI instance from the given options
     #
     # @param [Hash, Addressable::URI] options_or_uri

spec/lib/http/uri/normalizer_spec.rb

@@ -0,0 +1,95 @@
+# frozen_string_literal: true
+
+RSpec.describe HTTP::URI::NORMALIZER do
+  describe "scheme" do
+    it "lower-cases scheme" do
+      expect(HTTP::URI::NORMALIZER.call("HttP://example.com").scheme).to eq "http"
+    end
+  end
+
+  describe "hostname" do
+    it "lower-cases hostname" do
+      expect(HTTP::URI::NORMALIZER.call("http://EXAMPLE.com").host).to eq "example.com"
+    end
+
+    it "decodes percent-encoded hostname" do
+      expect(HTTP::URI::NORMALIZER.call("http://ex%61mple.com").host).to eq "example.com"
+    end
+
+    it "removes trailing period in hostname" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com.").host).to eq "example.com"
+    end
+
+    it "IDN-encodes non-ASCII hostname" do
+      expect(HTTP::URI::NORMALIZER.call("http://exämple.com").host).to eq "xn--exmple-cua.com"
+    end
+  end
+
+  describe "path" do
+    it "ensures path is not empty" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com").path).to eq "/"
+    end
+
+    it "preserves double slashes in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com//a///b").path).to eq "//a///b"
+    end
+
+    it "resolves single-dot segments in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/a/./b").path).to eq "/a/b"
+    end
+
+    it "resolves double-dot segments in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/a/b/../c").path).to eq "/a/c"
+    end
+
+    it "resolves leading double-dot segments in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/../a/b").path).to eq "/a/b"
+    end
+
+    it "percent-encodes control characters in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/\x00\x7F\n").path).to eq "/%00%7F%0A"
+    end
+
+    it "percent-encodes space in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/a b").path).to eq "/a%20b"
+    end
+
+    it "percent-encodes non-ASCII characters in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/キョ").path).to eq "/%E3%82%AD%E3%83%A7"
+    end
+
+    it "does not percent-encode non-special characters in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/~.-_!$&()*,;=:@{}").path).to eq "/~.-_!$&()*,;=:@{}"
+    end
+
+    it "preserves escape sequences in path" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/%41").path).to eq "/%41"
+    end
+  end
+
+  describe "query" do
+    it "allows no query" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com").query).to be_nil
+    end
+
+    it "percent-encodes control characters in query" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/?\x00\x7F\n").query).to eq "%00%7F%0A"
+    end
+
+    it "percent-encodes space in query" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/?a b").query).to eq "a%20b"
+    end
+
+    it "percent-encodes non-ASCII characters in query" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com?キョ").query).to eq "%E3%82%AD%E3%83%A7"
+    end
+
+    it "does not percent-encode non-special characters in query" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/?~.-_!$&()*,;=:@{}?").query).to eq "~.-_!$&()*,;=:@{}?"
+    end
+
+    it "preserves escape sequences in query" do
+      expect(HTTP::URI::NORMALIZER.call("http://example.com/?%41").query).to eq "%41"
+    end
+  end
+end